[Incoherence as an interaction phenomenon. Results of a single case study].
Traditionally psychiatric patients' change of topic occurring in interviews e.g. with a doctor are construed as a psychopathologically relevant type of incoherence (formal thought-disorder). In a single case study it can be shown, however, that more than half of the patient's changes of topic occur after a specific class of interactionally meaningful paraverbal features. These may be interpreted as signals of the patient's being ready to relinquish the speaker's role. Therefore, rather than interpreting this type of change of topic as thought-disordered incoherence it should be considered as a consequence of the patient's unsuccessful trying to take over the listener's role. In contrast to interactively unmarked (thought-disordered) changes of topic the occurrence of this phenomenon may be determined by the asymmetric doctor-patient relationship.